Detection of the key steps during Liquid Resin Infusion manufacturing of a polymer-matrix composite using an in-situ piezoelectric sensor

This article investigates the interest of a novel promising approach, dealing with the use of an in-situ piezoelectric (PZT) disk to monitor the whole manufacturing process of a glass fiber/polyester Polymer-Matrix Composite (PMC) plate using the Liquid Resin Infusion (LRI) technique. The real-time in-situ Process Monitoring (PM) is conducted using the electrical signature (capacitance) variation of the embedded PZT transducer, which has never been done so far in the literature for such a purpose. In order to understand the capacitance response, an internal/external multi-instrumentation (Infrared Thermography, thermocouples, Acoustic Emission, Z-displacement and pressure sensing devices) was set on the infusion systems, so that it was possible to make multi-physical couplings between the various obtained measurements and the PZT capacitance curves. It was shown that the PZT capacitance is sensitive to all several steps of the infusion process, especially the gelation and vitrification phases, and can also have Structural Health Monitoring (SHM) applications as it makes the resulting composite part ``smart''.